Miniature switch



Feb. 25, 1958 J. P. SHANLEY MINIATURE SWITCH Filed June es, 1956 3 2 I 4 4 4 4 4 V 4 &Q A uihniiuniuiiiui. M R I M E; N

UnitCd {States atntO MINIATURE swrrcn John P. Shanley, Oakland, N. J., assignor to Control l;rotlucts Inc., Harrison, N. 1., a corporation of New ersey Application June 6, 1956, Serial No. 589,677

I 6 Claims. (Cl. 200-138) This invention relates to switches, and more particularly to a miniature, thermal switch which may be manufactured as a hermetically sealed, rugged, compact unit eificient and durable in operation, more particularly described below and illustrated in the accompanying drawings, wherein:

Fig. l is a top plan view of a device embodying the invention, partly broken away,

Fig. 2 is a vertical sectional view taken on line 2-2 of Fig. 1,

Fig. 3 is an end elevational view taken on line 3-3 of Fig. l,

Fig. 4 is a vertical sectional view taken on line 4-4 of Fig. l,

Fig. 5 is a fragmentary, perspective view of an elongated contact spring which may be used in carrying out the invention,

Fig. 6 is a sectional view showing a terminal sealed in a mounting stud, pursuant to the invention, and

Fig. 7 is a fragmentary, elevational view of another form of switch embodying the invention.

As shown in the drawings, the device of this invention comprises a casing 10 (Fig. 3) provided with mounting lugs 11, 12 of any suitable form, and with the two-wire terminals 13, 14 hermetically sealed therein as, for example, by sealing glass 17, 18 in the mounting studs 15, 16 secured to the casing to provide hermetically sealed connections. In a preferred form of invention, the casing 10 comprises a bottom plate 19 to which the contact members 20, 21 are secured as, for example (Fig. 1) by passing anchor portions 22, 23 of said contact members through slots or recessed portions in an insulation block 24 fixed to member 19 by rivets 25, 26. Insulation block 24 may consist of halves 27, 28 (Fig. 4) slotted if desired, to receive the anchor portions 22, 23 of contact members 20, 21. The bottom 19 and associated parts described may be assembled as a single unit, and the bottom may have a heat conducting area to which one end of a temperature sensitive arm 30 may be directly mounted by securing it to the end portion 31 (Fig. 4) of a plate 33 secured to such heating conducting area of the bottom 19 (or, as shown in the drawings, said bottom 19 may be made of metal or other heat conducting material and plate 33 secured directly thereto).

In the preferred form of invention, the top of the casing (cover 29) and the bottom wall 19 and side walls 34 are made of metal, and the cover hermetically sealed to the side walls. The interior of the device may be cleared of all gaseous impurities and, if desired, filled with a sealing gas.

The large area of the bottom 19 cases is found to be very effective in transmitting temperature changes to the arm 30, directly mounted thereon. Thus, for example, ambient temperature changes or temperature changes directed against the device or against the bottom 19 will immediately and automatically operate the device responsive thereto.

Contact member comprises an elongated contact 2,824,933 Patented Feb. 25, ess

spring arm fixed as at one end, 36, to the casing, and having a free end 37 engaging the temperature sensitive arm 30, to thereby normally dispose the contact spring at a given position in the casing, as, for example, shown in full lines in Fig. 1, illustrating use of the invention in a normally open switch, and in Fig. 7 illustrating its use as a normally closed switch. The temperature sensitive arm 30 is thus disposed within the casing for movement responsive to temperature changes to which the heat conducting area of the casing is exposed. A fixed contact member 21 is provided having a portion 39 disposed at a predetermined position relative to the given normal position of the contact spring 20 so that on movement of the temperature sensitive arm '30 responsive to temperature changes, the spring contact arm 20 will'rnove from its given (normal) position, and, on the restoration of said normal temperature condition, will return thereto. If in the use of the invention as a normally open switch (Fig. 1) the movement of the temperature sensitive arm 30, and therefore the spring contact 20 responsive to temperature change is in a counter clockwise direction as indicated by arrow A, in use of the invention as a normally closed switch (Fig. 7) movement of the arm 30 and the spring contact member 20 will be in the counter clockwise direction of the arrow B (Fig. 7).

The elongated contact spring 20 is tensioned for constant engagement with arm 30 so that the device is always spring loaded. The difference in direction of flexing rotation of arm 30, and therefore of the spring contact 20 tensioned thereagainst responsive to temperature change in the Fig. 1 and Fig. 7 form may be attained for example, by disposing the high expansion side of the temperature sensitive arm 30 toward or away from wall 34. The free end of temperature sensitive arm 30, engaged by the free end 37 of elongated contact spring 20, may have an insulator 40 secured thereto as shown in the drawings.

The side walls 34 of the casing are preferably relatively shallow. The temperature sensitive arm 30 and contact members 20, 21, are of less height than the side wall and are medially mounted for free movement in operation of the device, as above described. Contact spring 20 is preferably of substantial length and disposed in a given plane, and may have the free end thereof 37 bent to define a finger terminating at a point spaced from said plane and engaging the temperature sensitive arm. Calibration means 41 (Figs. 1 and 2) may be provided, including a housing 42 secured to the wall 34 of the casing, provided with a slit end 43 inwardly of the casing and internally threaded, as at 44, wherein calibration means such as screw 45 may be reciprocated by a suitable tool, so as to dispose the inner end 46 of said screw (said inner end may be an insulation cap as shown in Fig. 2) against the portion 39 of the contact member 21, for adjustment of the position of said contact member relative to the other contact mem ber 20. Spring member 20 is preferably disposed in generally parallel relation to the temperature sensitive arm 30.

From the foregoing, it will be apparent that, pursuant to the invention, a miniature two wire (not grounded on one side) thermal switch is provided which may be truly hermetically sealed and which will, it has been found, withstand greatly elevated temperatures at which many temperature switches become impractical or inoperative. The feature of mounting the bimetallic arm 30 directly on the heat absorbing surface for control of the switch is a highly useful one. Calibration screw 45 is self locking, as shown in Fig. 2. The contact arms 20, 21 are spring loaded at all times-whether open or closed.

I claim:

1. A thermal switch comprising a casing, an elongated thermostatic member secured, at one end, to said casing and movable in the casing, a contact mounted in said casing, in spaced relation to the elongated thermostatic member, and an elongated contact spring secured, at one end, to said switch and extending from said end generally parallel to the elongated thermostatic member and intermediate and in spaced relation to said thermostatic member, and contact terminals in said switch connected to said contact and spring member, and means on said spring member engaging the thermostatic member whereby said spring member will selectively move into and out of engagement with the contact, in accordance with the rnovcment of the thermostatic member, responsive to temperature changes to which the casing is subjected.

2. In a thermal switch as set forth in claim 1, the end of the spring opposite the secured end thereof being bent to define a finger engaging the temperature sensitive arm and constituting the means on the spring member.

3. In a thermal switch as set forth in claim 2, an insulation element secured to the thermostatic element for engagement by the free end of the spring finger.

4. Ina thermal switch as set forth in "claim '1, means engaging the contact to adjust its point of location relative to the spring.

5. In a thermal switch as set forth in claim 1, means engaging the portion of the second contact so disposed at a predetermined position for adjustment of said predetermined position.

6. In a thermal switch as set forth in claim 1, an insulation block secured within the casing 'said elongated contact spring being so fixed to said block and thereby to the casing and said second contact being secured to the block and thereby so mounted in "said casing.

2,767,284 Moksu Oct. 16, 1956 

